PLEUROBRANCHUS. 195 



Jaws composed of lozenge-shaped pieces, each terminating in a 

 single denticle (pi. 74, fig. 96). Radula with the formula 150.0.150, 

 the lateral teeth bearing 8 to 10 small denticles immediately below 

 the terminal hook (pi. 74, fig. 95). 



Shell haliotiform, quite strong, translucent and iridescent; spire 

 little projecting; color amber yellow; under the microscope a close 

 pattern of longitudinal wrinkles is visible (fig. 63); these giving the 

 iridescent effect. 



Alt. 8, diam. 5 mill. ; alt. 7, diam. 4 mill. ( Vayssiere). 



Adriatic and Mediterranean Seas, laminarian and coralline zones ; 

 St. Lucie, Cape Verde Is. (Bouvier) ; Strait between Pico and Fayal, 

 Azores, 130 meters (Hirondelle). 



Pleurobranchus stellatus Risso, Hist. Nat. Eur. Merid., iv, p. 41 

 (1826). ROCHEBR., Nouv. Arch, du Mus., 1881, p. 264. 



Pleurobranchus ocellatus DELL.E CHIAJE, Memorie, Atlas, pi. 104, 

 f. 9, 16 (1828). 



P.plumula VAYSSIERE, Journ. de Conch., 1880, p. 208, pi. 7,f.2 

 (shell); Rech. Moll. Opistobr., Tectibranches, p. 113, f. 105-107 

 (teeth and jaws). MONTEROSATO, Journ. de Conch., 1874, p. 281. 

 BERGH, Camp. Sci. Albert I, fasc. iv, p. 19, pi. 2, f. 43-50 ; pi. 3, f. 

 51-67 ; and ? ? Bull. Mus. Comp. Zool. xxv, no. 10, p. 197, pi. 9, f. 

 12-14 ; pi. 10, f. 1-8 (from Lower California! ). Not P. plumula 

 Mont. 



Lamellaria Jcleciachi BRUSINA, Contr. Faun. Dalrn., p. 35 (1866). 



I retain the Mediterranean form separate from that of northern 

 Europe mainly on account of the great differences in jaws and den- 

 tition. In this species the elements of the jaw have a median point 

 but no lateral denticles, and the lateral teeth have numerous short 

 denticles below the terminal booklet. In P. plumula, as figured by 

 Sars, the plates of the jaw are multidenticulate, and the lateral teeth 

 apparently lack denticulation. There are also some differences in the 

 shells and gills between the two forms. 



The synonymy given is merely tentative. 



P. AURANTIACUS Risso. PI. 52, figs. 76, 77, 78, 79, 80. 



Body ovoid ; general color transparent orange, sometimes bright 

 orange; tissues very delicate. Mantle small, not covering either 

 buccal veil, rhinophores or end of the foot. Foot nearly twice as 

 long and as wide as the mantle. Gill pinnate, folded longitudin- 

 ally, quite long and with 16 or 17 pinnules on each side. Genital 

 orifices and anus as usual in the subgenus. 



Length 31; breadth 17 mill. 



